3-Position Pneumatic Actuator

Description of HPA Series 3 Position Pneumatic Rotary Actuator

The 3-position pneumatic actuator available in standard 0°–45°–90° and 0°–90°–180° configurations, offered in both Double Acting (DA) and Spring Return (SR) options. Built-in auxiliary pistons stop the main rack at a set middle angle. By splitting valve travel into fast filling and slow shut-off steps, it protects pumps and flow meters from sudden line shock while keeping filling cycles short.

Specifications & Features

100% Repeatable Mechanical Stop: Internal auxiliary pistons physically block the main pistons at the middle angle. Because it stops against a solid mechanical bolt rather than balanced air pressure, the valve will not drift from pipe vibration or supply pressure drops.

Externally Adjustable Mid-Angle:  Outside travel bolts let technicians adjust the middle stop angle, but only upward (above 45° or 90°). If your application requires a smaller angle (such as 20° or 30°), please let us know when ordering so we can set it at the factory.

Independent End-Stroke Adjustment: Independent stop screws provide ±5° travel adjustment at both fully closed (0°) and fully open positions (90° or 180°), allowing maintenance teams to set exact disc seating on-site for tight shut-off.

Prevents Pipe Shock and Tank Overflow: Allows fast bulk filling at full open, then drops to a low flow rate at the middle stop before final shut-off. This two-stage action prevents pipeline water hammer and stops liquid from splashing or overflowing.

Direct PLC Digital Control: Controls all three positions using standard ON/OFF solenoid valve circuits and digital 24VDC/PLC signals. Achieves reliable multi-stage filling without requiring smart positioners, 4–20mA analog cards, or complex loop tuning.

Standard ISO 5211 and NAMUR Fit: The bottom flange matches ISO 5211 patterns (F05–F14) to mount straight onto ball, butterfly, and plug valves without extra brackets. Top drive and air ports follow NAMUR standards to fit standard limit switch boxes and solenoid valves.

HPA Series Pneumatic Actuator Certificates: ISO 9001, CE, ATEX, SIL3, EAC and IP67

Optional Accessories Available: Solenoid valve · Limit switch box · Manual override gearbox · Air filter regulator

Direct OEM Customization: We offer full OEM service directly from our factory for valve distributors and wholesalers. You can choose custom actuator housing colors (RAL matching), stainless steel nameplates or label stickers with your brand logo and part numbers, and neutral or custom box packaging with reliable 15–25 day lead times.

Dual Hard-Anodized Protection: Housings and Pistons

All 3-position pneumatic actuators come standard with hard-anodized aluminum housings and pistons to handle frequent contact with internal mechanical stops and protect dynamic seals from wear.

Specification	Ordinary Anodizing	Hard Anodizing (Standard)
Coating Thickness	5 – 25 µm	25 – 50 µm (Industrial Standard)
Surface Hardness	200 – 300 HV	350 – 700 HV
Wear Resistance	Standard	Heavy-Duty / High Abrasion
Designed Duty	Light-duty / Low-cycle	10 Bar / 1-Million Cycles
Best For	General protection	High-cycle multi-position operation
Surface Treatment Options: Choose housing and piston treatments to match your operating environment and target cost: Untreated (Raw Aluminum): Bare aluminum for buyers focused on entry-level tender pricing in clean air setups. Ordinary Anodizing: Standard bath creating a thin oxide layer to protect actuator bodies and pistons from storage corrosion. Hard Anodizing: Our factory standard. Adds a thick, wear-resistant coating across 3-position actuator housings and pistons to stop seal abrasion, prevent internal air leaks, and resist cylinder scratching during mid-travel stops.

Construction & Engineering Specifications

3-position pneumatic actuators withstand higher mechanical loads than standard models because of intermediate stops and dual-stage pistons. We build each component with thick-wall aluminum profiles and precision machining to handle repeated stop impacts:

Extended Stroke & Center Cylinder Length: Rotation angle sets piston stroke and body length. For the same bore size, a 0°–90°–180° model requires a much longer extruded center cylinder than a 0°–45°–90° model. This extended stroke requires significantly more aluminum and longer precision machining, making 0°–90°–180° configurations naturally heavier and higher in manufacturing cost.	Full-Thickness Aluminum Walls: Main pistons create strong mechanical impacts when striking intermediate stops at 45° or 90°. To keep the long cylinder body from flexing or distorting over time, Hearken 3 position pneumatic actuator use heavy, full-thickness extruded aluminum walls. Combined with standard hard anodizing, this structural strength prevents internal air leaks and keeps midpoint stops accurate.	Dual Auxiliary End Assemblies & Drive Pinions: Each 3 position pneumatic actuator adds two auxiliary body extensions, dual-stage pistons, dynamic seal sets, and stainless steel travel stop bolts. Drive pinions are precision-machined from solid alloy steel with electroless nickel plating (ENP) to resist sudden stopping torque without gear damage. Custom shaft extension heights and specialized valve connections (such as milled Double-D or keyed drives) are available to match specific valve stems directly.

Customization Options – HPA Series 3 Position Pneumatic Rotary Actuator

Stroke Adjustment Rods		Top Drive Shaft Options	Manual Override Integration	End Caps
With External Rods (Adjustable)	Without External Rods	HPA Series Standard NAMUR Shaft	HPA+3-Position Declutchable Manual Override Gearbox	Custom End Caps (No Mold Required)
External stop rods on both sides for adjusting the middle angle from the outside.	No external rods on either side. Uses internal stops to keep a fixed angle and save space.	Standard NAMUR top drive fitted with a removable visual pointer. For mounting switch boxes or positioners, simply remove the indicator cap to access the standard NAMUR drive slot and screw holes.	Optional dedicated 3-position declutchable gearbox sandwich-mounted between actuator and valve. Features mechanical travel stops for precise multi-point positioning (0°–45°–90° / 0°–90°–180°), ensuring safe manual operation during commissioning or air supply failure.	Flexible OEM customization with embossed or debossed brand logos directly on aluminum end caps. Eliminates mold fees, making it cost-effective for small-batch private labeling and fast project delivery.

Indicator Types								Adjust Screws
regular				option				External Hex Head Screws	Hex Socket Set Screws / Grub Screws	Socket Head Cap Screws

Working Principle & Air Control

Principle Of Control

1. Full close position Air drawn in from port B, exhausted from port A.	2. Full open position Air drawn in port A and C, exhausted from port B and D.	3. Middle position Air drawn in from port A and D, exhausted from port B and C. The air pressure of port D forces the auxiliary piston to move to middle position until arrival of the limit position set by adjusting bolt.

Double Acting (DA) 3 Position Pneumatic Actuator Working Principle

0° -45° -90°/0° -90° -180° Three Position Pneumatic Actuator

The angle of the middle position can be field-adjusted upward using the external stop bolts (e.g., from 45° up to 50°/75°, or 90° up to 120°/150°). Angles smaller than the factory baseline (such as 20° or 30°) must be preset at our factory.

The operation of a three position pneumatic actuator requires the design of an electromagnetic valve control circuit system to complete the operation.The control principle is as follows.

Positioner 1 (Middle Position) The air supply pressure enters ports 2 and D simultaneously,and the air is discharged from ports 4 and C.Port 2 moves as an internal piston, while Port D restricts the positioning of the internal piston in the predetermined middle position through an auxiliary piston push rod.   Positioner 2 (Fully Open Position) The air source pressure enters ports 2 and C simultaneously,and the air is discharged from ports 4 and D.The internal piston of port 2 continues to move.Port C is used to release the limit positioning of the auxiliary piston push rod,allowing the internal piston to reach the fully open position smoothly.   Positioner 3 (Fully Closed Position) The air source pressure enters port 4,and air is discharged from port 2.The internal piston moves in the middle direction to reach the fully closed position.We can provide models and specifications for 0° -45° -90° spring return,which can force the internal piston to return to the fully closed position through the spring in the event of a power outage(or air source failure).

Spring Return (SR) 3 Position Pneumatic Actuator Working Principle

0° -45° -90° Stroke Spring Return Actuator

The 90° spring return 3 position pneumatic actuator is designed with spring components at both ends,suitable for reciprocating operation between 0° -45° -90° It returns to the 45°position through the spring in case of loss of air supply pressure (or malfunction).In the fully open position of 90° and fully closed position of 0°, it can be accurately adjusted ±5° externally in a standard manner.

From 45° To 90° When the air source pressure enters the middle chamber of the two pistons in the cylinder from the air port(2),it causes the two pistons to separate and move towards both ends of the cylinder, forcing the spring groups at both ends to compress.The air in the air chambers at both ends is discharged through the air port(4),and at the same time,the two piston racks synchronously drive the output shaft (gear) to rotate counterclockwise to 90°.   From 45° -0° When the air source pressure enters the air chambers at both ends of the cylinder from the air port(4),it causes the two pistons to move towards the middle direction of the cylinder, forcing the spring groups at both ends to compress.The air in the middle air chamber is discharged through the air port(2),and at the same time,the two piston racks synchronously drive the output shaft(gear)to rotate clockwise to 0°   Operation From Loss Of Air Supply Pressure When the position is at 90°: When air pressure is lost at the air port(2)or the solenoid valve is de-energized,the spring thrust forces the piston to move towards the middle of the cylinder,resulting in a clockwise rotation to the 45°position.Whent he position is at 0°:When air pressure is lost at the air port(4)or the solenoid valve is powered off,the spring generates thrust to force the piston to move towards both ends of the cylinder,causing counterclockwise rotation to the 45°position.

Materials and Component

Applications

A 3 position pneumatic valve actuator automates ball, butterfly, and plug valves for multi-stage fluid handling. It delivers dual-speed shutoff to stop liquid hammer in filling lines, and accurate 3-way diversion across chemical batching and tank transfer systems.

Compatible Valves

Typical Industrial Applications

Hearken HPA Series 3 Position Pneumatic Rotary Actuator Production Process

As a 3 position rack and pinion actuator manufacturer, our production follows a standardized machining and assembly flow. We CNC-machine the extruded aluminum housing, then assemble the multi-piston cylinders for precise intermediate position stopping. Before packing, every 3 position actuator undergoes 100% air-leakage testing and middle-stop angle calibration to ensure dependable batch consistency.

Step 1: Raw Material Sourcing & Cylinder Sawing	Step 2: Precision CNC Multi-Port Machining	Step 3: Housing & Alignment Inspection	Step 4: Precision Deburring & Surface Cleaning
We inspect incoming aluminum extrusions for wall thickness, alloy density, and surface quality. To match the extended travel requirements and intermediate stop design of 3-position actuators, we cut each cylinder profile to exact batch lengths with clean, square edges.	Multi-axis CNC centers machine the internal bores, mounting flanges, and multi-port air channels. We hold tight tolerances on stop cavities and secondary air passages to prevent internal leakage and ensure smooth multi-stage movement.	Every machined body is inspected using bore gauges and thread tools. We verify internal bore roundness, center pinion alignment, and stop-screw thread depth to ensure tight seal seating and smooth angle adjustments during assembly.	Every machined cylinder and auxiliary chamber undergoes manual and mechanical deburring. We remove sharp edges, burrs, and machining debris to protect piston seals from scoring and ensure proper adhesion during subsequent surface treatment.
Step 4: Hard Anodizing & Cylinder Bore Check	Step 5: Assembly	Step 6: Underwater Air Leak Testing	Step 7: IP67 Waterproof & Dust Testing
Housing and pistons of 3-position pneumatic actuators are hard-anodized to 45–50 μm (350–700 HV). This step extra auxiliary pistons constantly hit the mid-stop position, which easily scratches raw aluminum and causes air leaks. Bore roughness (Ra ≤ 0.4 μm) and coating depth are then verified before assembly.	Pistons, drive racks, seals, and the pinion shaft are greased and installed into the cylinder body. The extended end caps and external adjustment sleeves are then bolted on to complete the full 3-position actuator assembly.	Each 3-position pneumatic actuator is submerged in water and pressurized across all air ports to confirm zero bubble leakage across internal chambers.	High-pressure water jets and fine dust spray test the outer seals for 30 minutes. Inspection confirms zero water or dust gets past the extended adjustment screws, travel bolts, or drive shaft into the body.
Step 8: Output Torque & Switching Cycles	Step 9: Solenoid Valve Response Testing	Step 10: Factory Test Report	Step 11: Safe Export Packaging
Automated test stands cycle each 3-position pneumatic actuator through mid-position and full-stroke operations. Output torque for the rack and pinion drive is measured at 0°, intermediate hold (45° or 90°), and full-open positions under standard operating air pressure to ensure reliable valve opening.	Each 3-position pneumatic actuator connects to dual pilot solenoid valves to test electrical switching signals and air flow paths. This confirms auxiliary stop pistons move instantly without sticking, delayed response, or angle overshoot during mid-position holds.	Every 3-position pneumatic actuator includes an official test report. It records the serial number, set stop angles, pressure hold results, and real output torque for each actuator.	Each 3-position pneumatic actuator is packed with custom foam to protect the extended end caps and external adjustment screws. Actuators are then placed in strong wooden boxes to prevent damage and shaft bending during sea shipping.